1. Field of the Invention
This invention relates to an automatic focusing device in a stereoscopic microscope having an objective lens common to left and right stereoscopic observation optical systems of the stereoscopic microscope, and is particularly best suited for a microscope for use in surgical operations.
2. Description of the Prior Art
As a system for detecting the in-focus position of a microscope, there are known (1) a system which utilizes air pressure to make constant the distance between the end of an objective lens and a stage, (2) a system which moves a stage to a position whereat the contrast of the image on a focusing screen becomes maximum, and (3) a system which moves a stage so as to correct any variation in the light path of the reflected light of a light beam applied to a sample.